Add an Option to Disable the Mailing Lists Page

[kpu23]

People are concerned about the personal information shown on the Mailing Lists page. Although we do not store this data in the plugin, it is readable and also is cached in a transient.

I think two options should be added here:

(1) An option to disable this page completely

(2) An option to not use transients when fetching personal data

These options would give users more peace of mind when dealing with personal data.